@gooba42@bear_lab I would use a spline rather than hex, because it preserves the circular reference. I was thinking keyway, but a spline is basically a bunch of fixed keyways. Essentially the same idea.
I think the robust tooling you are referring to is a broach? (I've been designing inexpensive rotary broach holders lately.)
There could be a mashup of your and my ideas here: Use retaining compound to hold a male spline section on the motor shaft, then ream and broach the matching female spline on the pulley. It would then still be removable and adjustable, but couldn't really slip.
Commercial spline rotary broaches are hundreds of dollars, and a cheap commercial rotary broach holder is $500, most over $1000.
This could be fine with either rotary broaches or linear arbor broaches, and would be easy because it would be made with aluminum.